/*
 * Copyright 2008, Denis Zjukow.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.jemframework.domain;

public abstract class AbstractRelation<SourceType extends Entity, PublicTargetType extends Entity> implements Relation {

  private final SourceType iSource;

  public AbstractRelation(SourceType aSourceObject) {
    if (aSourceObject == null) {
      throw new NullPointerException();
    }

    iSource = aSourceObject;
  }

  public abstract void update();

  protected abstract boolean isBidirectional();

  protected void updateTarget(PublicTargetType aTarget) {
    if (!isBidirectional()) {
      throw new UnsupportedOperationException("It is not allowed to call updateTarget() method on a unidirectional relation.");
    }
  }

  protected void resetTarget(PublicTargetType aTarget) {
    if (!isBidirectional()) {
      throw new UnsupportedOperationException("It is not allowed to call updateTarget() method on a unidirectional relation.");
    }
  }

  protected SourceType getSource() {
    return iSource;
  }
}
